C++ Program to Deque - Double Ended Queue with Explanation
C++
Hard
STL
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1 min read
193 words
This problem helps you practice core C++ fundamentals in a practical way. It builds intuition around add, deque, remove. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Add/remove from both front and back.
Real Life: Line where you can join from either end.
Input Format
No user input.
Operations are performed on a deque (double-ended queue).
Output Format
Elements of deque after add and remove operations.
Constraints
• Use deque concept
• Add and remove allowed from both ends
Concept Explanation
A deque (double-ended queue) allows insertion and deletion
from both front and back.
This is like a line where people can join or leave from either end.
Step-by-Step Logic
1.Create a deque.
2.Add element at front using push_front().
3.Add element at back using push_back().
4.Remove element from front using pop_front().
5.Remove element from back using pop_back().
6.Print remaining elements of deque.
Code Solution
This explanation is written for learning purposes and to help beginners understand the concept clearly.
void stl_q13_deque() {
deque<int> dq;
dq.push_back(20);
dq.push_back(30);
dq.push_front(10);
dq.push_front(5);
cout << "Deque: ";
for(int num : dq) {
cout << num << " ";
}
cout << endl;
dq.pop_front();
dq.pop_back();
cout << "After removing from both ends: ";
for(int num : dq) {
cout << num << " ";
}
cout << endl;
}
Output Example
Input:
Add 10 at front
Add 20 at back
Add 5 at front
Remove from front
Remove from back
Output:
Deque elements: 10
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Solution Guide
Problem
Add/remove from both front and back.
Real Life: Line where you can join from either end.
Input / Output
Input
No user input.
Operations are performed on a deque (double-ended queue).
Output
Elements of deque after add and remove operations.
Constraints
• Use deque concept
• Add and remove allowed from both ends
Examples
Input:
Add 10 at front
Add 20 at back
Add 5 at front
Remove from front
Remove from back
Output:
Deque elements: 10
Explanation
Concept Explanation
A deque (double-ended queue) allows insertion and deletion
from both front and back.
This is like a line where people can join or leave from either end.
Step-by-Step Explanation
1.Create a deque.
2.Add element at front using push_front().
3.Add element at back using push_back().
4.Remove element from front using pop_front().
5.Remove element from back using pop_back().
6.Print remaining elements of deque.
Details
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Official Solution
void stl_q13_deque() {
deque<int> dq;
dq.push_back(20);
dq.push_back(30);
dq.push_front(10);
dq.push_front(5);
cout << "Deque: ";
for(int num : dq) {
cout << num << " ";
}
cout << endl;
dq.pop_front();
dq.pop_back();
cout << "After removing from both ends: ";
for(int num : dq) {
cout << num << " ";
}
cout << endl;
}
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